JPH0363027B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for verifying the ground insulation performance of a grounded tank type gas insulated disconnect switch when the charging current is interrupted.

Charging current disconnection tests for gas insulated disconnectors are usually performed by configuring a circuit that is approximately equivalent to the on-site circuit.

FIG. 1 shows an example of this. An AC power source 2 is connected to one end of the disconnector 1 via a gas insulated bus 5, and a disconnector 4 is attached to the opposite end via a gas insulated bus 3. The circuit configuration is such that a gas insulated bus bar 6 is further connected to the tip of the breaker 4. Here, when the disconnector 4 becomes open, the load side voltage _Vl of the disconnector 1 becomes a circuit in which only the capacitance _Cl of the _gas insulated bus 3 is added to the power supply side voltage Vs. . When the disconnector 1 is opened here, the charging current of the capacitance C _l is suddenly cut off. FIG. 2 shows the transition of the power supply side voltage V _s and the load side voltage V _l when the charging current is interrupted.

The disconnector opens at time t _s , repeats re-ignition and re-ignition, and completes the disconnection at t ₀ . At the time of restriking, a surge voltage is generated as shown in the figure, and in particular, as shown in the figure, when restriking between the peak values of the AC voltage, a surge voltage of 2.5 pu occurs.
Surge voltages up to a considerable amount (n = 2.5) may occur. As a disconnector, it must satisfy ground insulation even under such conditions. However, in such tests, the situation at the time of final restriking differs for each test, and the generated surge voltage fluctuates in a complicated manner, so it takes an extremely large number of tests and a great deal of expense to satisfy the conditions that can occur on site. There are drawbacks that require

As a way to solve this problem, a test method has been devised in which a circuit as shown in FIG. 3 is constructed and the period from time t ₁ to t 2 shown in FIG. ₂ is simulated. This method is a circuit in which bushings 10 and 11 are arranged at both ends of a disconnector 1, a power supply 20 and a capacitor 22 are connected to the bushing 10 side, and another power supply 21 and a capacitor 23 are connected to the other bushing 11 side. This is done through configuration. The power supply 21 is a DC voltage generator for simulating the load side voltage V _l in FIG.
These are impulse voltage generators or half-wave AC voltage generators for simulating _Vs. In this test, the distance between the poles of the disconnector is set to correspond to the maximum arc length when the charging current is interrupted, and a DC voltage corresponding to the peak value of AC is applied from the power source 21. After that, a rising voltage corresponding to 1/4 waveform of the AC voltage with the opposite polarity to that of the power source 21 is applied from the power source 20 to simulate the most severe restriking situation and verify the ground insulation under the surge voltage generated at this time. It's a method. According to this method, it is possible to perform sufficient verification tests by selecting only the most severe conditions, but the test requires two high-voltage power supplies and two high-voltage bushings. The disadvantage is that the equipment is large-scale. In particular, in the case of ultra-high voltage (UHV), which has been developed in recent years, the scale has become even larger and the testing costs have become enormous.

An object of the present invention is to provide a method that is simpler and allows verification of insulation to ground when a disconnector charging current is disconnected using small-scale equipment.

The present invention has experimentally confirmed that the discharge time constant of the gas insulated bus bar is sufficiently large, and by charging the gas insulated bus bar by electrode-to-electrode discharge, DC voltage remains on the gas bus bar, thereby replacing the DC voltage generator in the conventional method. I decided to omit it. That is, since the test involves applying voltage only from one side of the disconnector, bushing only needs to be present on one side of the disconnector.

An embodiment of the invention is shown in FIG. A gas insulated bus bar 3 is connected to one side of a disconnector 1 housed in a grounded tank to form a load. A bushing 10 is attached to the other side of the disconnector 1, and a lead wire 26
It is connected to the power supply 20 by. Note that voltage dividers 24 and 25 are provided to measure the voltages V _s and V _l on the power supply side and load side of the disconnector 1. Also,
Between the capacitance C _l of the gas-insulated bus on the load side and the equivalent capacitance C _s on the power supply side, C _s is C _l to simulate the actual system.
The value is set to be at least one order of magnitude larger than . In such a circuit configuration, when the distance between the poles of the disconnector 1 is set to a certain value and a voltage is applied from the power source 20, a voltage waveform as shown in FIG. 5 is obtained at a voltage above a certain value. The upper part of Fig. 5 shows the power supply side voltage V _s , which is applied at time t ₀ and discharges between the electrodes mentioned above at t ₁ , and the DC load side voltage V _l as shown in the lower part is applied to the load side gas insulated bus 3. It becomes a residual form.
The discharge time constant of this residual voltage is determined by the capacitance C _l of the load side gas insulated bus bar 3 and the insulation resistance of the spacer 7 etc. that insulates and supports the high voltage conductor 9. Generally, the insulation resistance of spacers used in gas-insulated equipment is extremely high compared to that in the atmosphere, so the above-mentioned discharge time constant is on the order of several hours to several days. In other words, as long as the test is carried out within several tens of minutes, it is safe to assume that the charging voltage is maintained as it is. Note that since a normal capacitor is placed in the atmosphere, the time constant is quite short. With this method, it is possible to apply any DC voltage to the load side by appropriately changing the distance between the poles of the disconnector and the applied voltage, so there is no need to provide a separate DC power source as in conventional methods. .

FIG. 6 shows details of the disconnecting section of the grounded tank type disconnector. A movable electrode 32 and a fixed electrode 33 are arranged in a grounded tank 30, and shields 31 and 34 for mitigating the electric field are attached around them.

The ground insulation performance of a disconnector with such an inter-electrode length L when the charging current is interrupted is determined by the performance against restriking surges at the position of the movable electrode where the arc length is the maximum. As mentioned above, the restriking surge is the highest at the restriking between the peak values of the positive and negative polarities of the alternating current. In other words, for performance verification, separate the poles of the disconnector by a predetermined distance, apply DC voltage to the load side,
By applying a voltage of the same level and opposite polarity from the power supply side, a discharge is caused between the electrodes, and the insulation to ground is verified at that time.

In this method, first, in order to cause a predetermined DC voltage to remain in the load, V ₁ and V ₂ are respectively applied from the power supply side in a state where the distance between poles is L ₁ or L ₂ as shown in FIG. 7. In this case, if the relationship between the inter-electrode length L and the flashover voltage V is determined in advance as shown in FIG. 7, this will serve as a guideline for the residual DC voltage. By such a method, a predetermined DC voltage remains on the load side, and then the distance between the poles is increased to a length corresponding to the maximum arc length, etc. Subsequently, the polarity of the power supply is switched so that it is opposite to the polarity of the DC voltage that already remains, and a predetermined voltage is applied. FIG. 8 shows the voltage waveform at this time. Due to the remaining load side voltage V _l and the power supply side voltage V _s applied at time t ₃ , the gap between the disconnector poles flashes over at time t ₄ . This situation corresponds to the final restrike (time t ₁ ~
t ₂ ), and it is possible to verify the ground insulation based on the surge voltage V _n that occurs at this time. Note that the power supply voltage waveform is 1/1 of the AC voltage.
It is most preferable to use a rising waveform corresponding to four cycles, but it is also possible to verify ground insulation using a waveform in the switching impulse region.

With this method, the test can be performed using one power supply and one bushing, so the same verification test as in the past can be performed using a small-scale test device.

In the above-mentioned method, control of the DC residual voltage on the load side has to depend on the distance between the movable electrode and the fixed electrode, which causes large fluctuations. The reason for this is that the structure of a disconnector is generally asymmetrical, which causes a polarity effect on the discharge, and even if a discharge is caused between the electrodes, depending on the polarity, a reverse flash (discharge to the power supply side due to residual DC voltage) or This is because discharge occurs due to dark current. To improve this, the first discharge is carried out with a polarity that is unlikely to cause discharge due to reverse flash or dark current, so that the DC voltage of that polarity remains on the load side, and then the length between the poles is increased to generate the voltage of the opposite polarity. If applied, it becomes possible to sufficiently retain polarity that is likely to cause reverse flash faults and the like. That is, if a polarity that is likely to cause reverse flash is to remain on the load side, it is necessary to perform a discharge in advance with a polarity that is unlikely to cause reverse flash, so the number of discharges required to remain once increases.

A method to further improve this will be described below.

FIG. 9 shows a window 40 provided on the side of a grounded tank 30, and an irradiation device (mercury lamp, laser oscillator, etc.) 4.
1 makes it possible to irradiate radiation between the electrodes 32 and 33. FIG. 10 shows the discharge characteristics between the electrodes with and without irradiation. At the same pole length L, the discharge voltage (FOV) can be lowered from V ₀ to V ₁ by irradiation. That is, by performing irradiation at the wave front of the applied voltage, discharging at a sufficiently low voltage, and stopping the irradiation at the wave tail, it is possible to improve the discharge voltage and prevent reverse flash and the like. Note that it is preferable to make the wave tail length sufficiently long so as not to leave any influence of irradiation on the wave tail.

In FIG. 11, the inside of the tip of the movable electrode 32 is hollowed out, and a trigger electrode 51 is attached using an insulating support 50. In this structure, a potential difference is generated between the trigger electrode 51 and the movable electrode 32 due to capacitance partial pressure at the wave front of the applied voltage, and as a result of discharge between the two, this is used as a trigger to cause an interelectrode discharge to occur at a low voltage. becomes possible. Once the residual charge is discharged, it becomes a DC electric field, so that no potential difference is generated between the trigger electrode 51 and the movable electrode 32 as described above, and it is possible to prevent reverse flash faults and the like as in the case described above.

In the above method, it becomes easy to prevent reverse flashover after residual DC voltage or discharge due to dark current, so that the residual DC voltage can be easily controlled, and the efficiency of the test is improved.

According to the present invention, it is possible to verify the insulation to the ground when the charging current of a disconnector is cut off using a small-scale facility with a single power supply, so the higher the rated voltage of the disconnector, the greater the effect of its application. Especially in the UHV class, bushings are very expensive, so this method is very effective as a test method that only requires one bushing.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an example of the conventional test method.
The figure shows an example of the voltage waveform in Fig. 1, Fig. 3 is a circuit diagram showing another example of the conventional test method, Fig. 4 is a circuit diagram showing an embodiment of the present invention, and Fig. 5 is the same as in Fig. 4. Examples of voltage waveforms, Figure 6 is a detailed cross-sectional view of a disconnector, Figures 7 and 8 are characteristic diagrams showing the test principle of the present invention,
FIG. 9 is a sectional view showing another embodiment of the present invention, the first
FIG. 0 is a characteristic diagram showing the test principle, and FIG. 11 is a sectional view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Disconnector, 2...AC power supply, 3,5,6...Gas-insulated busbar, 4...Shin breaker, 7...Spacer, 8...Center conductor, 9...Grounding tank, 10,11...Butching, 20,21 ...Power supply, 22, 23...Capacitor, 30...Grounding tank, 31,34...Shield,
32...Movable electrode, 33...Fixed electrode, 40...Window, 4
DESCRIPTION OF SYMBOLS 1... Irradiation device, 50... Insulating support, 51... Trigger electrode.

Claims (1)

[Claims] 1. A disconnector consisting of a movable electrode and a fixed electrode is arranged in a grounded tank, a capacitive load is connected to one side of the electrode, and a capacitive load is connected to the other electrode. Connect the power supply, first set the distance between the electrodes of the disconnector to the length determined by the relationship with the flashover voltage, and apply the first voltage from the power supply to discharge between the electrodes. A voltage remains in the capacitive load, and then the distance between the electrodes of the disconnector is increased to a distance corresponding to the maximum arc length, and a second voltage is applied from the same power source side with a polarity opposite to that of the first voltage. A charging current and ground insulation verification test method for a disconnector, characterized in that by applying a second voltage, a discharge is caused between the electrodes to verify the ground insulation. 2. The disconnector according to claim 1, characterized in that the distance between the movable electrode and the fixed electrode during the second voltage application is greater than the distance between the electrodes during the first voltage application. Ground insulation verification test method when charging current is interrupted. 3. Verification of charging current and ground insulation during breakage of a disconnector according to claim 1, characterized in that radiation is irradiated between the movable electrode and the fixed electrode when applying the voltage for the first time. Test method. 4. A testing method for verifying insulation to ground when charging current is interrupted in a disconnector according to claim 1, characterized in that an insulated and supported trigger electrode is attached to the tip of the movable electrode or the fixed electrode. 5. According to claim 1, the disconnector is characterized in that the capacitive load is a gas-insulated bus bar with a center conductor supported by an insulating spacer in a grounded tank. Insulation verification test method. 6. According to claim 1, the charging current of the disconnector is characterized in that the equivalent capacitance of the power source is one order of magnitude or more larger than the capacitance of the capacitive load. Insulation verification test method.